Conventional two-way communication systems may separate transmit (Tx) and receive (Rx) signals at each device from one another in at least one of frequency, time, and space.
For example, in a conventional frequency division duplex (FDD) communication system, frequency separation may be used to separate Tx and Rx signals. In a single carrier (also called single channel) configuration, communication between a network and a user device such as a wireless transmit/receive unit (WTRU) may use two frequency bands, one in the uplink (UL) for communication to the network and one in the downlink (DL) for communication from the network. Enough spacing may be provided between the UL and DL channels to permit filters to adequately attenuate energy from the transmitted signal that may leak into the received signal.
In a conventional time division duplex (TDD) system, time separation may be used to separate Tx and Rx signals. In a single carrier (or single channel) configuration, communication uses a single band which is shared in time between UL and DL. However in full duplex (FD) systems a channel may be used to transmit and receive the radio frequency (RF) signal simultaneously.